Re: Answer the 1Million Question: Where is the air ride control relay located?

The compressor is most likely shot. You can leave the jumper in the relay socket and check if you have power at the round plug right beside the compressor. If you do plan on removing the compressor and replace it.

Re: Answer the 1Million Question: Where is the air ride control relay located?

it has to be sagging, its really not easy to see it, but if you measure it, you'd be surprised. When my shocks are manually filled with air, it sits 3.5" higher than when I hook up my trailer with no air.

Manually pump air via the relay jumper take some measurements from the tow hitch to the ground. Drive around for a little bit to get rid of some air and then hook the trailer up and measure agin.... you'll notice a big change. Its hard to see by eye.

Re: Answer the 1Million Question: Where is the air ride control relay located?

Any more progress? I have the exact same problem with my ESV as does my buddy with his Denali. We swapped SCM's, but that didn't help. Probing the light blue wire at the SCM will activate the compressor, but that's as far as we got so far.

Re: Answer the 1Million Question: Where is the air ride control relay located?

Good to know! I don't have access to another SCM for that test. I'm gonna look into this tonight, no check engine light on for the last week, time to move on to another issue... Good idea to measure from the hitch receiver to the ground! I also didnt notice the sagging from the back end till I started reading the forums here and realizing the air compressor is supposed to raised the back end automatically.

All above data collected with ignition on and suspension at zero PSI pressure. I disconnected the 2 sensors for the rear level indicators by unscrewing the 10mm pivot of the rod at the sensor itself. Both are registering within range (0.5 - 4.8Volts). From what I observed, I could not get the exhaust solenoid to do anything by applying ground to B5 (DK BLUE) at the PNK connector. Either with compressor on or off, it doesnt affect the output of air to the shocks. For reference, I manually (I got a switch inside the cab) activated the compressor for about a minute, with key on, here's the data from that test:

I find those value a bit on the low end of the scale. The back end of the truck was waaaay high, heck it looked like a souped-up cheapo pinto wagon ready for the dragstrip! I can't really picture how the system can reach the high end of the position+pressure sensors.

So far all checks ok. I'm starting to fear the worst! This will definately require a trip to sumone with a Tech2 scanner to clear DTC's. I might have a code stored in memory from the worn out shocks, thats preventing the system from functionning... I'm gonna sleep on it

Re: Answer the 1Million Question: Where is the air ride control relay located?

you really think stored codes would prevent the scm from funcitioning? it makes sense since the dealers want you to bring the car in for service... interesting... i never thought about that.... im still waiting on my buddy to see if he can get me an appointment with his friend/service manager at the chevy dealer...

i will test everything again over the weekend, i been swamped with work.... hopefully sunday i will get a chance to do the tests, but im pretty sure everything is in check. You got me thinking about the stored code issue....

I was under the impression that a run time of more than 5 minutes from the compressor witout any change in the air pressure sensor's output or a change in the level height, would result in a DTC and disabling of the ALC system. Actually the compressor does shut down, but only till the next time the ignition is cyled off and then on. I'm pretty sure all is well with those 3 codes. Then I found this info, on top of every diagnostic for the ALC, you gotta clear DTC C0870 first, which is reference voltage to all sensors,including the dreaded steering position sensor! Here is the info:

DTC C0870
Circuit Description
The Electronic Suspension Control (ESC) module provides a common regulated voltage of approximately 5 volts to all four of the body-to-wheel suspension position sensors, air pressure sensor and the steering handwheel position/speed sensor. The ESC module monitors this reference voltage for any malfunctions that could prevent it from outputting a regulated 5 volts.

Conditions for Running the DTC
Continuously with the ignition on.

Conditions for Setting the DTC
The ESC module senses a sensor reference voltage of less than 4.0 volts or greater than 6.0 volts.

Action Taken When the DTC Sets
Disable all EVO outputs. Disable all compressor leveling functions, and assume default pressure.
Disable all suspension damper solenoid outputs.
The SERVICE RIDE CONTROL message will be displayed.
Stores a DTC C0870 in the ESC module memory.
Conditions for Clearing the DTC
The ESC module senses the correct voltage output to the suspension position sensors upon the next ignition cycle.
Using a scan tool.
A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
Diagnostic Aids

Important
Ignition cycle counting is used by the ESC module to detect faults in the system. The objective is to eliminate false/intermittent codes while maintaining an acceptable level of system performance. The operation of the ignition cycle counting requires that a fault condition be present for four consecutive ignition cycles before it will set the fault code and display the "SERVICE RIDE CONTROL" message. If a fault code is present (without a fault being current), the system will go into one or more degraded modes without displaying a message. Resetting the ignition cycle counter is done by clearing codes with a scan tool. Clearing codes will override ignition cycle counting for one ignition cycle. Therefore, a fault condition will set the fault code immediately if it occurs on the first ignition cycle after the codes are cleared.

The following conditions may cause a malfunction to occur:
A short to voltage in any one of the body-to-wheel suspension position sensor reference voltage circuit.
A short to ground in any one of the body-to-wheel suspension position sensor reference voltage circuit.
If the circuit is shorted to ground, the scan tool will display all suspension position sensor voltage as zero.
If the circuit is shorted to an unwanted voltage source, the scan tool may display all suspension position sensor voltage as that voltage.
A short to voltage in the 5 volt reference of the air pressure sensor.
A short to ground in the 5 volt reference of the air pressure sensor.
A short to voltage in the 5 volt reference of the steering handwheel position/speed sensor.
A short to ground in the 5 volt reference of the steering handwheel position/speed sensor.
A intermittent malfunction or DTC may cause a random firm/soft ride condition.
Test Description
The numbers below refer to the step numbers on the diagnostic table.

Tests all suspension position sensors reference voltage circuits.

Tests the 5 volt reference circuit of the steering handwheel position/speed sensor for a short to ground and a short to voltage.

Tests the 5 volt reference circuit of the air pressure sensor for a short to ground and a short to voltage.

1
Did you perform the RTD Diagnostic System Check?
Go to Step 2
Go to Diagnostic System Check - Real Time Damping

2
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With a scan tool, observe the suspension position sensors, air pressure sensor, and steering wheel position sensor 5 volt reference data parameters in the ESC module data list.
Does the scan tool indicate that all the above mentioned data parameters are less than 4 volts or greater than 6 volts?
Go to Step 3
Go to Diagnostic Aids

3

Test all 4 body-to-wheel suspension position sensor 5 volt reference circuits for a short to ground and a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 7
Go to Step 4

4
Test the steering handwheel position/speed sensor 5 volt reference circuit for a short to ground and a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
Go to Step 7
Go to Step 5

5
Test the air pressure sensor 5 volt reference circuit for a short to ground and a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

7
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
Go to Step 2
System OK

This code will disable the ALC. I included a pic of the old shocks I removed, and the SCM module with ID beside the plugs for easier troubleshooting.

I stopped by another GM dealer (non-cadilllac) where I got my parts for my Blazer K5 build. They will scan and check the SCM for $35. Not too bad... I wanted to borrow the Tech 2 scanner on site, they didnt want... I'll wait for the outcome from your scan session before going that route.

Re: Answer the 1Million Question: Where is the air ride control relay located?

Wiring diagram of the steering input module:

For the sake of science, I unplugged the SCM and turned the ignition on, yipeee a new error message, service ride control!!! There is communication happening afterall... I was worried my out of commission EBCM would overide all error messages (except low fuel level). I will attempt to fool the SCM into thinking all reference 5 volts is ok, if I can find where to do so. I can't see where that reference voltage is for the pressure sensor? More updates to come...